Patent GB-1377874-A (GB)
Title: Method and system for purification of internal combustion engine exhaust gases
IPC: F01N13/02
Filed: 1972-03-30
Abstract: 1377874 Purifying I C engine exhaust gases CHEMICAL CONSTRUCTION CORP 30 March 1972 [5 April 1971 27 April 1971 28 Jan 1972] 15046/72 Heading F1B Exhaust gases supplied to a manifold 106 flow in sequence through catalyst zones 118 and 120 and oxygen, e.g. pure oxygen or air is supplied to the manifold and zone 120 in accordance with the value of a variable, e.g. catalyst or exhaust gas temperature, carbon monoxide or nitrogen oxides exhaust composition, time or mass of exhaust gases emitted from starting. The zone 118 contains a catalyst for the reduction of nitrogen oxides by reducing gases, e.g. carbon monoxide and hydrogen and the zone 120 contains a catalyst for the oxidation of carbon monoxide and hydrocarbons. The atmosphere in the zone 118 is one containing greater than one volume per cent of reducing gases and insufficient oxygen to prevent nitrogen oxides reduction and the atmosphere in zone 120 is one with oxygen in excess of the stoichiometric requirement e.g. a 30% excess. The catalyst in zone 118 is preferably also an oxidation catalyst. The exhaust gases leaving the zone 120 are from 5 to 20% e.g. 10%, recirculated to the engine air filter 102 or to the intake manifold and exhaust gases upstream of the zone 118 may be cooled by heat exchange with the atmosphere in passing through a pipe loop 204a. Air may be supplied by a vane pump 115, belt driven from the engine crank-shaft, through valves 201 and 202 in lines 127 and 129. The valves 201 and 202 and the valves 203 and 204, respectively controlling recirculation and cooling are controlled in accordance with one or more predetermined temperatures sensed by thermostats 134, 148 in the zones 118, 120 or thermostats in the inlet to the zone 118, between the zones and in the outlet of the zone 120 in accordance with the temperature difference between adjacent thermostats. A thermometer (14), Fig. 1A (not shown), may indicate the sensed temperature. Below a predetermined sensed temperature, e.g. 440‹F in the zone 120 or 650‹F. in the zone 118, the valve 201 is open with the valves 202, 203 closed and the valve 204 by-passing the loop 204a. Above the predetermined temperature or a further predetermined temperature, e.g. 650‹F in zone 118, the valves 202, 203 are opened or the valve 203 is opened at the further predetermined temperature. At further predetermined temperatures, e.g. 1450 or 1550‹F and 1600 or 1700‹F, respectively, valve 204 causes flow through the loop 204a and the valves 202 and 203 or 201, 202 203 to be closed. The valve 204 or valves controlling cooling may be in the exhaust pipe 122 or the loop 204a and provide cooling when the predetermined temperature, e.g. 1450 or 1550‹F, is exceeded and until the temperature falls to a predetermined lower value. The valves 201 ... 204 may be operated by solenoids controlled by thermocouple energized relays or solenoid-operated valves may control the application of intake manifold vacuum to valve actuators. The valves may be operated by a computer in accordance with the rate of change of a sensed variable. With air-flow blocked a diaphragm-operated pressure relief valve 141 vents the pump output. With the valve 202 open the proportions of air flowing to the manifold 106 and zone 120 are in a ratio of 30:70 to 5:95, preferably 20:80 to 90:10. A reducing agent, e.g. carbon monoxide, propane or petrol, may be introduced into the exhaust gas upstream of the zone 118. The air supply to the manifold 106 may include passages within the engine block terminating adjacent the exhaust ports or conduits entending into the manifold and the air supply may be continuous or controlled intermittently with the exhaust port opening and closing. Separate pumps may supply the manifold 106 and zone 120 or the air may be supplied from a container. The engine of piston or Wankel type may have a carburetter or fuel injection. The catalyst zones 118, 120 may be in separate reactors or a single reactor with annular cylindrical or conical beds with the second zone outwardly of and at least partly overlapping the first zone. The catalyst may be platinum or nickel, cobalt, manganese or copper, as the metal, oxides or salts or mixtures thereof on alpha, eta or gamma alumina, kaolin or silica as a support. The support may be a refractory oxide or silicate honeycomb. Examples of the preparation of catalysts of CuO, Co 2 O 3  and MnO 2  on alumina cylinders and spheres and the use of this catalyst in the zone 118 and platinum on alumina in the zone 120 are given in the Specification together with reactor sizes and weights of catalyst employed.